Transistors used in power electronic applications have typically been fabricated with silicon (Si) semiconductor materials. Common transistor devices for power applications include Si CoolMOS, Si Power MOSFETs, and Si Insulated Gate Bipolar Transistors (IGBTs). While Si power devices are inexpensive, they can suffer from a number of disadvantages, including relatively low switching speeds and high levels of electrical noise. More recently, silicon carbide (SiC) power devices have been considered due to their superior properties. III-Nitride or III-N semiconductor devices, such as gallium nitride (GaN) devices, are now emerging as attractive candidates to carry large currents, support high voltages, and to provide very low on-resistance and fast switching times.
Forming ohmic contacts to III-N material structures, which are utilized in many devices, is often achieved by depositing one or more metal layers on the III-N material and then annealing the structure, causing the metals and underlying III-N material to intermix and form an alloy. While such an alloying process for forming ohmic contacts has been shown to successfully result in low-resistivity ohmic contacts, the reliability and yield of this process has typically been lower than required for commercial scale production.